#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<unistd.h>
#include<sys/types.h>
#include<sys/wait.h>

using namespace std;
const int basesize = 1024;
const int argvnum = 64;
const int envnum = 64;

//全局的命令行参数
char *gargv[argvnum];
int gargc = 0;

int lastcode = 0;
//我的系统的环境变量
char* genv[envnum];

//全局的工作路径
char pwd[basesize];
char pwdenv[basesize];

string GetUserName()
{
    string name = getenv("USER");
    return name.empty() ? "None" : name;
}

string GetHostName()
{
    string hostname = getenv("HOSTNAME");
    return hostname.empty() ? "None" : hostname;
}

string GetPwd()
{
    // char pwd[basesize];
    if(nullptr == getcwd(pwd,sizeof(pwd))) return "None";
    snprintf(pwdenv, sizeof(pwdenv), "PWD=%s",pwd);
    putenv(pwdenv); 
    return pwd;
    
    //string pwd = getenv("PWD");
    // return pwd.empty() ? "None" : pwd;
}

string LastDir()
{
    string curr = GetPwd();
    if(curr == "/" || curr == "None") return curr; 
    size_t pos = curr.rfind("/");
    if(pos == std::string::npos) return curr;
    return curr.substr(pos+1);
}

string MakeConmandLine()
{
    char Command_line[basesize];
    snprintf(Command_line,basesize,"[%s@%s %s]# ",\
            GetUserName().c_str(),GetHostName().c_str(),LastDir().c_str());
    return Command_line;
}

void PrintCommandLine()
{
    printf("%s", MakeConmandLine().c_str());
    fflush(stdout);
}

bool GetCommandLine(char command_buffer[], int size)
{
    char *result = fgets(command_buffer,size, stdin);
    if(!result)
    {
        return false;
    }
    command_buffer[strlen(command_buffer) - 1] = 0;
    if(strlen(command_buffer) == 0) return false;
    return true;
}

void ParseCommandLine(char command_buffer[], int len)
{
    (void) len;
    memset(gargv,0,sizeof(gargv));
    gargc = 0;
    //"ls -a -l -n"
    const char *sep = " ";
    gargv[gargc++] =  strtok(command_buffer,sep);
    
    while((bool)(gargv[gargc++] = strtok(nullptr, sep)));
    gargc--;
}

void debug()
{
    printf("argc: %d\n", gargc);
    for(int i = 0; gargv[i];i++)
    {
        printf("argv[%d]:%s\n", i, gargv[i]);
    }
}

bool ExecuteCommand()
{
    // 让子进程进行执行
    pid_t id = fork();
    if(id < 0)
    {
        return false;
    }
    else if(id == 0)
    {
        //子进程
        //1.执行命令 2.退出exit
        execvpe(gargv[0], gargv,genv); 
        exit(1);
    }
    int status = 0;
    pid_t rid = waitpid(id,&status,0 );
    if(rid > 0)
    {
        if(WIFEXITED(status)) //判断子进程是否正常退出
        {
            lastcode = WEXITSTATUS(status);
        }
        else
        {
            lastcode = 100;
        }
        return true;
    }
    return false;
}

void AddEnv(const char *item)
{
    int index = 0;
    while(genv[index])
    {
        index++;
    }
    genv[index] = (char*)malloc(strlen(item)+1);
    strncpy(genv[index],item,strlen(item)+1);
    genv[++index] = nullptr;
}

//shell自己执行命令
bool CheckAndExecBuiltCommand()
{
    if(strcmp(gargv[0],"cd") == 0)
    {
        if(gargc == 2)
        {
            chdir(gargv[1]);
            lastcode = 0;
        }
        else
        {
            lastcode = 1;
        }
        return true;
    }
    else if(strcmp(gargv[0], "export") == 0)
    {
        if(gargc == 2)
        {
            AddEnv(gargv[1]);
            lastcode = 0;
        }
        else
        {
            lastcode = 2;
        }
        return true;
    }
    else if(strcmp(gargv[0], "env") == 0)
    {
        for(int i = 0; genv[i]; i++)
        {
            printf("%s\n",genv[i]);
        }
        lastcode = 0;
        return true;
    }
    else if(strcmp(gargv[0], "echo") == 0)
    {
        if(gargc == 2)
        {
            if(gargv[1][0] == '$')
            {
                if(gargv[1][1] == '?')
                {
                    printf("%d\n", lastcode);
                    lastcode = 0;
                }
            }
            else
            {
                printf("%s\n",gargv[1]);
                lastcode = 0;
            }
        }
        else
        {
            lastcode = 3;
        }
        return true;
    }
    return false;
}

void InitEnv()
{
    extern char** environ;
    int index = 0;
    while(environ[index])
    {
        genv[index] = (char*)malloc(strlen(environ[index])+1);
        strncpy(genv[index],environ[index],strlen(environ[index])+1);
        index++;
    }
    genv[index] = nullptr;
}

int main()
{
    InitEnv();
    char command_buffer[basesize];
    while(true)
    {
        PrintCommandLine(); //1.命令行提示符
        //printf("\n");
        //sleep(100);
        //command_buffer 输出型参数
        if (!GetCommandLine(command_buffer, basesize)) //2.获取用户命令
        {
            continue;
        }
       //printf("%s\n",command_buffer);
       ParseCommandLine(command_buffer,strlen(command_buffer));//3.分析命令

       //debug();

       if(CheckAndExecBuiltCommand())
       {
           continue;
       }

       ExecuteCommand(); //4.执行命令
    }
    return 0;
}
